Company Merriam-Webster, Inc. created these great apps:
Merriam-Webster Dictionary, Merriam-Webster Dictionary HD, Merriam-Webster Dictionary+, Merriam-Webster Dictionary & Thesaurus HD, Learner's Dictionary - English, Learner's Dictionary - English HD, SCRABBLE Dictionary, Quizzitive – A Merriam-Webster Word Game, Puku: Learn New Words, and others..